[flutter_tools] change the IntelliJ plugin detection logic. (#68020)

This PR suggests improving the IntelliJ plugin "jar" detection logic.

Previously:
The IntelliJ Flutter plugin was contained flutter-intellij.jar.
Currently:
It is named flutter-intellij-X.Y.Z.jar and does not contain META-INF/plugin.xml.
META-INF/plugin.xml is included in flutter-idea-X.Y.Z.jar.

So this PR changes the rules for searching the plugin's jar file.
Concretely, it looks for the jar file containing META-INF/plugin.xml in the plugin's package directory and reads the package version from its META-INF/plugin.xml.
Co-authored-by: Jonah Williams <jonahwilliams@google.com>

packages/flutter_tools/lib/src/intellij/intellij.dart

@@ -15,6 +15,25 @@ import '../doctor.dart';
 /// This searches on the provided plugin path for a JAR archive, then
 /// unzips it to parse the META-INF/plugin.xml for version information.
 ///
+/// In particular, the Intellij Flutter plugin has a different structure depending on the version.
+///
+/// For flutter-intellij plugin v49 or lower:
+///   flutter-intellij/lib/flutter-intellij.jar ( includes META-INF/plugin.xml )
+///
+/// For flutter-intellij plugin v50 or higher and for Intellij 2020.2:
+///   flutter-intellij/lib/flutter-intellij-X.Y.Z.jar
+///                        flutter-idea-X.Y.Z.jar ( includes META-INF/plugin.xml )
+///                        flutter-studio-X.Y.Z.jar
+///
+/// For flutter-intellij plugin v50 or higher and for Intellij 2020.3:
+///   flutter-intellij/lib/flutter-intellij-X.Y.Z.jar
+///                        flutter-idea-X.Y.Z.jar ( includes META-INF/plugin.xml )
+///
+/// where X.Y.Z is the version number.
+///
+/// Intellij Flutter plugin's files can be found here:
+///   https://plugins.jetbrains.com/plugin/9212-flutter/versions/stable
+///
 /// See also:
 ///   * [IntellijValidator], the validator base class that uses this to check
 ///     plugin versions.
@@ -69,17 +88,61 @@ class IntelliJPlugins {
     return _fileSystem.isDirectorySync(packagePath);
   }
 
-  String _readPackageVersion(String packageName) {
-    final String jarPath = packageName.endsWith('.jar')
-        ? _fileSystem.path.join(pluginsPath, packageName)
-        : _fileSystem.path.join(pluginsPath, packageName, 'lib', '$packageName.jar');
-    final File file = _fileSystem.file(jarPath);
-    if (!file.existsSync()) {
-      return null;
+  ArchiveFile _findPluginXml(String packageName) {
+    final List<File> mainJarFileList = <File>[];
+    if (packageName.endsWith('.jar')) {
+      // package exists (checked in _hasPackage)
+      mainJarFileList.add(_fileSystem.file(_fileSystem.path.join(pluginsPath, packageName)));
+    } else {
+      final String packageLibPath =
+          _fileSystem.path.join(pluginsPath, packageName, 'lib');
+      if (!_fileSystem.isDirectorySync(packageLibPath)) {
+        return null;
+      }
+      // Collect the files with a file suffix of .jar/.zip that contains the plugin.xml file
+      final List<File> pluginJarFiles = _fileSystem
+          .directory(_fileSystem.path.join(pluginsPath, packageName, 'lib'))
+          .listSync()
+          .whereType<File>()
+          .where((File file) {
+            final String fileExt= _fileSystem.path.extension(file.path);
+            return fileExt == '.jar' || fileExt == '.zip';
+          })
+          .toList();
+
+      if (pluginJarFiles.isEmpty) {
+        return null;
+      }
+      // Prefer file with the same suffix as the package name
+      pluginJarFiles.sort((File a, File b) {
+        final bool aStartWithPackageName =
+            a.basename.toLowerCase().startsWith(packageName.toLowerCase());
+        final bool bStartWithPackageName =
+            b.basename.toLowerCase().startsWith(packageName.toLowerCase());
+        if (bStartWithPackageName != aStartWithPackageName) {
+          return bStartWithPackageName ? 1 : -1;
+        }
+        return a.basename.length - b.basename.length;
+      });
+      mainJarFileList.addAll(pluginJarFiles);
     }
-    try {
+
+    for (final File file in mainJarFileList) {
       final Archive archive = ZipDecoder().decodeBytes(file.readAsBytesSync());
       final ArchiveFile archiveFile = archive.findFile('META-INF/plugin.xml');
+      if (archiveFile != null) {
+        return archiveFile;
+      }
+    }
+    return null;
+  }
+
+  String _readPackageVersion(String packageName) {
+    try {
+      final ArchiveFile archiveFile = _findPluginXml(packageName);
+      if (archiveFile == null) {
+        return null;
+      }
       final String content = utf8.decode(archiveFile.content as List<int>);
       const String versionStartTag = '<version>';
       final int start = content.indexOf(versionStartTag);

packages/flutter_tools/test/general.shard/intellij/intellij_test.dart

@@ -69,6 +69,81 @@ void main() {
     expect(message.message, contains('recommended minimum version'));
   });
 
+  testWithoutContext('IntelliJPlugins can read the package version of the flutter-intellij 50.0+/IntelliJ 2020.2+ layout', () async {
+    final IntelliJPlugins plugins = IntelliJPlugins(_kPluginsPath, fileSystem: fileSystem);
+
+    final Archive flutterIdeaJarArchive = buildSingleFileArchive('META-INF/plugin.xml', r'''
+<idea-plugin version="2">
+<name>Flutter</name>
+<version>50.0</version>
+</idea-plugin>
+''');
+    writeFileCreatingDirectories(
+      fileSystem.path.join(_kPluginsPath, 'flutter-intellij', 'lib', 'flutter-idea-50.0.jar'),
+      ZipEncoder().encode(flutterIdeaJarArchive),
+    );
+    final Archive flutterIntellijJarArchive = buildSingleFileArchive('META-INF/MANIFEST.MF', r'''
+Manifest-Version: 1.0
+''');
+    writeFileCreatingDirectories(
+      fileSystem.path.join(_kPluginsPath, 'flutter-intellij', 'lib', 'flutter-intellij-50.0.jar'),
+      ZipEncoder().encode(flutterIntellijJarArchive),
+    );
+
+    final List<ValidationMessage> messages = <ValidationMessage>[];
+    plugins.validatePackage(messages,
+      <String>[
+        'flutter-intellij',
+        'flutter-intellij.jar',
+      ],
+      'Flutter', 'download-Flutter',
+      minVersion: IntelliJPlugins.kMinFlutterPluginVersion,
+    );
+
+    final ValidationMessage message = messages.firstWhere(
+            (ValidationMessage m) => m.message.startsWith('Flutter '));
+    expect(message.message, contains('Flutter plugin version 50.0'));
+  });
+
+  testWithoutContext('IntelliJPlugins can read the package version of the flutter-intellij 50.0+/IntelliJ 2020.2+ layout(priority is given to packages with the same prefix as packageName)', () async {
+    final IntelliJPlugins plugins = IntelliJPlugins(_kPluginsPath, fileSystem: fileSystem);
+
+    final Archive flutterIdeaJarArchive = buildSingleFileArchive('META-INF/plugin.xml', r'''
+<idea-plugin version="2">
+<name>Flutter</name>
+<version>50.0</version>
+</idea-plugin>
+''');
+    writeFileCreatingDirectories(
+      fileSystem.path.join(_kPluginsPath, 'flutter-intellij', 'lib', 'flutter-idea-50.0.jar'),
+      ZipEncoder().encode(flutterIdeaJarArchive),
+    );
+    final Archive flutterIntellijJarArchive = buildSingleFileArchive('META-INF/plugin.xml', r'''
+<idea-plugin version="2">
+<name>Flutter</name>
+<version>51.0</version>
+</idea-plugin>
+''');
+    writeFileCreatingDirectories(
+      fileSystem.path.join(_kPluginsPath, 'flutter-intellij', 'lib', 'flutter-intellij-50.0.jar'),
+      ZipEncoder().encode(flutterIntellijJarArchive),
+    );
+
+    final List<ValidationMessage> messages = <ValidationMessage>[];
+    plugins.validatePackage(messages,
+      <String>[
+        'flutter-intellij',
+        'flutter-intellij.jar',
+      ],
+      'Flutter', 'download-Flutter',
+      minVersion: IntelliJPlugins.kMinFlutterPluginVersion,
+    );
+
+    final ValidationMessage message = messages.firstWhere(
+            (ValidationMessage m) => m.message.startsWith('Flutter '));
+    expect(message.message, contains('Flutter plugin version 51.0'));
+  });
+
   testWithoutContext('IntelliJPlugins not found displays a link to their download site', () async {
     final IntelliJPlugins plugins = IntelliJPlugins(_kPluginsPath, fileSystem: fileSystem);
 
@@ -94,11 +169,8 @@ void main() {
     final IntelliJPlugins plugins = IntelliJPlugins(_kPluginsPath, fileSystem: fileSystem);
 
     final Archive dartJarArchive =
-    buildSingleFileArchive('META-INF/plugin.xml', r'''
-<idea-plugin version="2">
-<name>Dart</name>
-<version>162.2485</version>
-</idea-plugin>
+    buildSingleFileArchive('META-INF/MANIFEST.MF', r'''
+Manifest-Version: 1.0
 ''');
     writeFileCreatingDirectories(
       fileSystem.path.join(_kPluginsPath, 'Dart', 'lib', 'Other.jar'),